Document & Entity Information (USD $)	12 Months Ended			12 Months Ended
	Dec. 31, 2011	Jun. 30, 2011	Feb. 10, 2012 CMS Energy Corporation [Member]	Dec. 31, 2011 Consumers Energy Company [Member]	Feb. 10, 2012 Consumers Energy Company [Member]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2011
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2011
Trading Symbol	cms
Entity Registrant Name	CMS Energy Corporation			Consumers Energy Company
Entity Central Index Key	0000811156			0000201533
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer			Non-accelerated Filer
Entity Public Float		$ 4,927,343,315
Entity Common Stock, Shares Outstanding			258,570,812		84,108,789